• Need Shape Sets

Launch: Connecting to Prior Knowledge: Finding an acceptable mathematical definition for polygon turns out to be tricky. The basic idea is that a polygon is a closed figure consisting of line segments connected at the endpoints, called vertices. Additionally, starting at any vertex, the outline of a polygon can be traced completely without visiting any vertex more than once and by returning to the starting point. Since polygons consist of line segments, figures that are curved are not polygons. Figures that have line segments that intersect at any point other than a vertex are not polygons. Also, figures that are not closed cannot be polygons because they cannot be traced by returning to the starting point.

Quick Start Expectations1. Come in and sit quietly.2. Fill in planner and HWRS:

3. Work on Warm-up :

1. Give two equivalent fractions for 8 12

2. Insert < , >, or = to write a true statement: 11 3 38 26 6 21 12 4 38 26 13 41

Textbook: CMP3 Grade 7 Unit: Shapes and Designs

pp. 24-33: #2-4, 37-44, 46 (WS for #2)

How would you describe the difference between the two groups?

What test would you suggest for deciding if a figure is a polygon?

What familiar objects have shapes like the polygon examples?What other shapes could be used as examples of polygons and non-polygons?

Polygons are closed with straight sides;

Tracing the edges to get back to the start without retracing or crossing a line segment.

various road signs

Quadrilaterals and octagons are polygons. Semicircles and squiggles are non-polygons.

non-polygons can be open with curved sides.

Describe the key properties that define a polygon:

Closed figure

Consists of line segments (no curves)Connected by vertices (endpoints)

Starting at any vertex, the outline of a polygon can be traced completely without visiting any vertex more than one

and by returning to the starting point.

Group Activity:

Which polygon is it? a. One team member picks a polygon from the shapes bag.

b. Think about its properties. Without naming it, describe the shape including appropriate vocabulary:

vertex / verticesangleline segment

c. Other team members guess the correct polygon.d. Take turns describing and guessing.

As a team use the Shapes Set (shown on pg. 9)

to answer the questions on page 10. Record the answers in your journal.

ANSWERS:

Answers will vary.

Answers will vary.A – all sides and angles are equal (equilateral triangle)P – a pair of equal sides and equal angles (isosceles triangle)I and T – no equal sides or angles.

Amount of groups will vary, including rectangles, non-rectangle parallelograms, trapezoids, no parallel sides.

1. R, O, S have one pair of parallel sides (trapezoid)2. Q doesn’t have any parallel sides, but it is still a quadrilateral.

3. L has two sides of parallel sides – referred to as a parallelogram,but can be a trapezoid.

Squares & Rectangles• How are squares and rectangles the same?

They each have 4 sides and 4 angles.

• How are they different?A square must have 4 equal sides and 4 equal angles.Rectangles just need opposite sides equal and all angles equal.

• Is N a rectangle? Why or why not? No, because it does not have 4 right angles.

• Is a rectangle a parallelogram? Why or why not?Yes, it is a quadrilateral with opposite sides equal and opposite

angles of the same measure.

• Is a square a rectangle? Why or why not?Yes, not only are opposite sides equal, but all sides are equal.

Homework:Textbook: CMP3 Grade 7 Unit: Shapes and Designs pp. 24-33 #2-4, 37-44, 46Use WS for #2